\begin{table}%t2
%\centering
\par
\caption{\protect\label{tab_halo}
As Table~\ref{tab_zind}, but
with enhanced and reduced coronal diffusivities
($\eta_1=3$ and 0.3).
The asterisked entries  have $R_\alpha=0$, and refer to  purely
advective calculations, with no dynamo action.}
\begin{tabular}{lccll}
\hline\hline
$B_{\rm ext}$   &$E_{\rm t}\times10^{-4}$     &$E_{\rm d}\times10^{-4}$     &$s\times10^6$        &$\phzero F_0$ \\
\hline
\multicolumn{5}{c}{$\eta_1=3$}\\[3pt]
\phone0.0\phzero  &$5.0$               &$4.7$              &$\tphzero3.1$  &$\phzero\phzero0.35$  \\ %run240
\phone0.01        &$5.1$               &$4.8$              &$\tphzero3.3$  &$\phzero\phzero0.39$  \\ %run242
\phone0.03        &$5.3$               &$5.0$              &$\tphzero4.6$  &$\phzero\phzero0.49$  \\ %run247
\phone0.10        &$61\tphzero$        &$48\phzero\phzero$ &$\phzero17$    &$\phzero\phzero0.84$  \\ %run244
\phone1.0         &$33\tphzero$        &$26\phzero\phzero$ &$240$          &$\phzero\phzero5.6\phzero$  \\ %run245
10.0              &$3.6\times10^3$     &$2.1\times10^3$    &$230$          &$\phzero57\phzero\phzero$    \\ %run259
$*1.0$            &$36\tphzero$        &$0.2$              &$230\tphzero$  &$\phzero\phzero5.7$  \\ %run249
\hline
\multicolumn{5}{c}{$\eta_1=0.3$}\\[3pt]
\phone0.0        &$9.1$                 &$6.3$                 &$\tphzero2.7$ &$\phzero\phzero0.58$ \\%run250
\phone0.01       &$9.5$                 &$6.5$                 &$\tphzero2.9$ &$\phzero\phzero0.63$  \\ %run252
\phone0.1        &$14\tphzero\phzero$   &$8.3$                 &$\tphzero9.0$ &$\phzero\phzero1.1\phzero$  \\ %run255
\phone1.0        &$400\tphzero\tphzero$ &$120\tphzero\tphzero$ &$\phzero22$   &$\phzero\phzero8.3\phzero$  \\ %run255
10.0             &$4.5\times10^5$       &$1.1\times10^4$       &$\phzero20$   &$\phzero84\phzero\phzero$ \\ %run256
$*1.0$           &$450\tphzero\tphzero$ &$110\tphzero\tphzero$ &$\phzero20$   &$\phzero\phzero8.4\phzero$  \\ %run259
\hline
\end{tabular}
%\end{flushleft}
\end{table}